The present invention relates to portable battery-powered computers.
The Ongoing Downsizing of Portable Personal Computers
Portable personal computers were introduced in the early 1980s, and proved to be very useful and popular. As this market has developed, it has become increasingly clear that users strongly desire systems to have small volume, small weight, and long battery-powered lifetime. Thus, small portable computers ("laptop" computers) have proven extremely popular during the late 1980s. Users continue to demand more features, longer time between recharges, and lower weight and volume. This combination of demands is difficult to meet. Moreover, as of 1990, another smaller generation of portable computers has begun to appear, referred to as "notebook" computers. This smaller form factor will only exacerbate the difficulty of the above tradeoffs.
The Use of Standby Modes
Laptop computer systems will typically have an automatic power-down function. Since some of the components use significant power, even when no computation or input is occurring, the system will send itself into a standby or sleep mode if the user has not provided any input for a given period of time (e.g. 30 seconds or five minutes). (Sleep mode may not normally be entered, however, if new information is still being written to the display.)
There are various enhancements which have been proposed to the scheme. For example, it may be desirable to blank the display after a certain length of inactivity and shut down the system clock only after an additional length of inactivity.
Thus, there may be more than one reduced-power mode. For example, in the presently preferred embodiment a "standby" mode is used to transiently power-down subsystems (such as the display or the hard disk) without stopping the CPU. For deeper inactivity, a "sleep" mode can also be entered, in which nearly all functions of the system are turned off. From the standpoint of power consumption, entering sleep mode is almost the same as turning a conventional nonportable machine off (except that data will not be lost).
The Variety of Users' Work Habits
None of the known systems fully address the needs of differing users with differing work habits. For example, some users will frequently stop to think for a minute or two during the middle of a work session, and do not want their displays to blank. Some users are more prone to walk away at the end of a session without shutting down the computer. Some users have greater need to maximize the efficiency of battery usage, whereas other users are more concerned to avoid the inconvenience of having the display blank while in the middle of input.
Such work habits may vary, not only from user to user, but also from session to session. Many users have very different use patterns when running different applications. For example, a user may want to be able to examine a large spreadsheet screen without the screen being blanked; but the same user, while typing text into a word-processing application, may be fairly indifferent to screen blanking at any momentary pause.
Existing laptop computers have allowed some selection of the inactivity time-out period. This is usually done through the setup program, and the resulting parameters stored in the CMOS NVSRAM.
Automatic Temporary Adaptation to Varying Work Habits
The present invention provides a new advance in adaptation to the different needs of different users. The power management controller, in this embodiment, takes note of events where the user commands a power-up immediately or very soon after the system has powered itself down. If a power-up occurs within a short period after a power-down (e.g., a few seconds), the net power savings may be insignificant, and the user is likely to be irritated as well.
When such events occur, the time-out period is temporarily extended. The user, in the presently preferred embodiment, can still program in his choice of default parameter, and can also select whether the adaptive modification to be enabled or disabled. If the adaptive modification is enabled, the system will change its power conservation strategy to match the actual work pattern of the user.
Preferably this is implemented using a microcontroller, separate from the main processor, for power-management functions. Under certain conditions, this power-management microcontroller can take control of the system bus.
Note that this is also advantageous for guest users (i.e. users who are not the primary user of the PC they are on), or for novice users (who may not know how to change parameters in setup).